High oil pressure

[Andres Darvasi]

Since I bought my aircraft (10 month ago and 85 hrs) the oil pressure has been at the top of the green on the Piper gauge and at 90/92 in cruise on the engine analyzer. The former owner says that it was always like that.
Due to the oil leak that I had (it was the prop governor gasket) during my Caribbean trip, I started monitoring the oil pressure very closely, and I noticed that at some times it was up to 94/96. (hot engine, hot ambient temp)
Last weekend I flew to the beach right after changing oil and filter, and on Monday, after flying half an hour I landed to pick up my daughter at another location and at restart the oil pressure went into the yellow area of the gauge, and the engine analyzer showed 108 psi! The ambient temperature was around 80 degrees.
After take off it started going down to 96 for a while and kept going down to settle at 92/93 psi.
The filter and oil analysis of the last oil changed were clean.
I am going to take this new filter out and cut it (it has 4.5 hrs) and see how it is, but Im both puzzled and concerned.
Any advice, tips or actions suggested will be greatly appreciated.

[JIMICS2452]

Andres, it sounds like the oil pressure relief valve is sett too high. It would be something to have you mechanic look at.

I assume all else is well.

[Andres Darvasi]

Hi Jim,

It could very well be, but my concern was that there might be an oil passage blocked somewhere, however, if I understand the oil sequence correctly, the oil goes from the pump through the filter and then on to the crank case towards the from of the engine, therefore if there was a blocked oil passage the prop governor will be affected for lack of oil, and this is not the case.

The reasoning behind the oil passage concern comes from the increase in oil pressure at relatively low RPM (on the ramp) with a hot engine and fairly hot ambient temp.

Today I will change the filter which is only 4.5 hrs old, open it and see if there is any metal, then I will have the pressure reduced on the pressure relief valve.

[Andres Darvasi]

Well, this morning I changed the filter and cut it open, it is spotless!

The bloody oil relief valve is placed in such a way that needs at least a couple of hours work to get to it, so it was not done today.

I run the engine, not very long, but the oil temperature got to 80 degrees and the oil pressure was at 81psi at 800 rpm and 106 psi at 1300 rpm.

[Clarence Beintema]

There are two types of oil pressure relief valve on our engines. Both are in the upper right side of the engine behind cylinder five. The older style has no means of external adjustment, meaning that you have to remove it from the engine. Once removed you should find washers under the spring, remove some of the washers to,lower the pressure. Once you have the value where you are happy, remove it again, install a new copper gasket, reinstall and safety wire it.

If you,are lucky to have the externally adjustable version you simply need a 9/16" wrench, turning the nut to the left will lower the spring tension and lower the pressure.

Clarence

[Andres Darvasi]

Thank you Clarence, will try to do it next Saturday. I am afraid that to get there I will have to remove the baffling!

[BSAND47]

Recently, my freshly overhauled io-720 was installed and ground run. Oil pressure was measured at over 120 psi.

Shut down engine, adjusted oil pressure relief valve (by turning the nut) to softest setting, but still oil pressure stayed around 120 psi.

Lycoming makes 4 or 5 different springs for the valve, so we installed the next softest spring (which was a real pain, btw, since some of the baffles had to be removed to get to the valve).

That solved the problem as the oil pressure is in middle of the green arc, with room to adjust the
valve either to raise or lower the pressure from current setting, if desired.

The spring part number we used is 61084. Other spring part numbers are LW11713 (the stiff one we replaced), 68668, and 77467 (softest).


Bill

[Andres Darvasi]

Hello Bill,

Thanks for posting your findings.

I am still struggling with high oil pressure. I will wait until the annual to deal with it because it needs a lot of work to get to the valve.

I was checking the other day the records of my engine analyzer and discovered sporadic sudden jumps during cruise, which are unexplained, it may suddenly go from 90 to as high as 110 psi and then down again.

I have flown the aircraft only about 100 hrs in the last year since I bought it and the former owner says that it was always like that, however I do not feel comfortable with this situation.